Rocks at heart of renewable methane

2011 R&D 100 WinnerMethane is the primary component in natural gas, contributing a high specific energy. It burns cleanly and with low emission of carbon dioxide as compared to coal or petroleum. Unlike other fossil energy sources, methane can be produced by biological action of anaerobic digestion of many waste materials including manure, coal, or oil shale.

Argonne National Laboratory, Argonne, Ill., and Eurisko Scientific LLC, McClellan, Calif., have introduced an Enhanced Renewable Methane Production System for anaerobic digesters that sequesters carbon dioxide. The technique begins with the introduction of low-cost pulverized rocks, which are high in divalent minerals, into an anaerobic digestion system. These minerals neutralize the carbonic acid and precipitate them as insoluble carbonates, trapping the carbon dioxide. Intermediate organic acids are not affected by the pulverized minerals and the carbon dioxide does not evolve into the gas space.

The resulting methane is produced at more than 90% purity, which is closer to pipeline quality than prior methane production methods. In addition, the gas evolves at significantly higher production rates, reducing the overall footprint of the anaerobic digester.